A: WinDAM B models erosion in earthen embankments as well as erosion in earthen auxiliary spillways of dams. The three-phase erosion model was jointly developed by the Agricultural Research Service (ARS) and the NRCS.

1) Phase one of the erosion or failure process is failure of the vegetal cover and development of concentrated flow.

2) Phase two is downward erosion in the area of concentrated flow, resulting in headcut formation.

3) Phase three is downward and upstream movement of the headcut, potentially breaching the spillway or embankment.

Each phase is described by a set of threshold-rate relationships based on the process mechanics. A headcut erodibility index (Kh) describes the resistance of the exposed geologic materials to erosive attack during the third phase of the process.

Q: Where can I download some example data sets?
A: Twelve sample data sets, combined in one download file, demonstrate some of the WinDAM B features.
They are described in the table below the download button.

A: WinDAM B does not create a reservoir inflow hydrographs. The reservoir inflow hydrograph must be created outside of WinDAM B and imported or pasted into the input screen. Software from NRCS such as SITES or WinTR-20 can create the needed hydrograph. Software from other agencies or vendors such as Corps of Engineers HEC-HMS can also be used to create the reservoir inflow hydrograph.

WinDAM B hydraulically routes a single inflow hydrograph through the dam’s riser/conduit, auxiliary spillway, and over the embankment to create an outflow hydrograph.

A: WinDAM B software does not check the design for compliance with NRCS design criteria. The user must check the design. WinDAM B estimates the erosion in an earthen auxiliary spillway as well as the erosion from overtopping the earthen embankment. WinDAM B does not create a reservoir inflow hydrograph, it only imports an existing hydrograph. SITES software checks the site design against existing USDA-NRCS design criteria found in USDA-NRCS National Engineering Handbook Part 630 – Hydrology, Technical Release 60, and National Conservation Practice Standard 378 – Pond. SITES software estimates erosion in an earthen auxiliary spillway, but does not analyze embankment overtopping. SITES can create a hydrograph from basic hydrologic information such as: rainfall depth, rainfall distribution, rainfall duration, drainage area, and runoff curve number.

A: No, WinDAM B will not replace SITES. New features will continue to be added to the WinDAM series. SITES will be maintained (though not enhanced) as a design tool for NRCS engineers and others who want to use it.

Q: What kind of geotechnical information do I need for a WinDAM B analysis?

A: For a complete erosion estimate including the auxiliary spillway and earthen embankment, the geotechnical composition of these two features of the dam must be characterized. Typical parameters such as representative particle size, percent clay fraction, plasticity index, total unit weight, undrained shear strength, and critical shear stress. Specific to WinDAM B software, the headcut erodibility index (Kh) and detachment coefficient (Kd) also need to be estimated.

A: None. The Natural Resources Conservation Service, the Agricultural Research Service, and Kansas State University used government funds to develop the WinDAM B software. It may be downloaded for use and copying at no additional expense or license requirements.

Q: My dam doesn’t have grass growing on it. Can I still use WinDAM B software?

A: WinDAM B can estimate erosion if the dam slope is protected by vegetation, riprap, or is simply bare earth. WinDAM B does not handle other erosion protection measures such as articulated concrete blocks (ACB’s) or erosion matting products.